The present invention generally relates to capsules for containing beverage-forming ingredients, a beverage producing system for use in connection with such capsules as well as to methods for producing beverages using such capsules.
The background of the present invention is the field of capsules which are adapted to contain beverage or other comestible (e.g., soup) ingredients. By means of an interaction of these ingredients with a liquid, a beverage or other comestibles, such as for example soups, can be produced. The interaction can be for example an extraction, brewing, dissolution, etc. process. Such a capsule is particularly suited to contain ground coffee in order to produce a coffee beverage by having hot water under pressure enter the capsule and draining a coffee beverage from the capsule.
A capsule as shown in Australian patent application 51,220/73 relates to an apparatus for making coffee beverage from a cartridge in which a water injection device is placed hermetically against the upper side of the cartridge. The water injection device includes a seal which is applied on the upper rim of the capsule.
EP 0361569 A1 does not show a sealed capsule, but instead discloses a coffee filter unit which is not sealed when placed into the coffee machine but is simply press fitted in a cartridge casing, such that water can be poured on a filter paper provided at the open upper side of the coffee filter unit. To avoid spilling of water outside the filter unit's upper rim, the peripheral portion of a filter paper is clamped between the outer rim of the coffee filter unit wall and the surrounding wall of the machine. Such a design is an device filtering a beverage at atmospheric pressure which is not adapted to withstand the typical water injection pressure of e.g., more than 3 bars or even much higher pressure which reigns in the capsule when e.g. an espresso-style coffee is to be produced.
FR 2617389 describes a capsule-based coffee machine in which a capsule to be extracted is placed on a capsule holder. The capsule holder is then rotated bayonet-like, wherein the final rotational position depends on the torque which the user applies on a handle for rotating the capsule holder. The machine itself does therefore not have a defined closure position since the final closure position depends on the amount of torque applied by the user. The sealing between the capsule and the machine is therefore not defined by the design of the machine, but arbitrarily depends on the user's handling of the machine. Typically, the higher the rotational force exerted, the more clearance can be compensated. However, such system provides several drawbacks. First of all, it requires the closing device to remain purely tightened by hand and it cannot be otherwise mechanically, electrically or hydraulically assisted. It requires a certain strength to screw the capsule holder on the machine from the user and the user may have difficulties to unscrew the capsule holder afterwards. Furthermore, the sealing is difficult to control and it may be that the capsule holder is insufficiently tightened so that pressure leakage can occur.
In contrast to the rotational bayonet-style closing according to FR 2617389, the present invention relates to machines in which the closure of the parts of the machine which surround the capsule and thus also the sealing is not an arbitrary function of the user's force, but a defined state which depends on the arrangement of the capsule in the machine. This is, for example, the case in machines in which the final phase of the closure movement is essentially an axial (i.e., translational or a curvilinear) but non-rotational movement.
The systems and methods for obtaining fluid comestibles from substances containing capsules are for example known from U.S. Pat. No. 5,402,707. The capsule 101 as shown therein in FIG. 1 has a frustroconically-shaped cup 102 which may be filled e.g. with roasted and ground coffee 103 and which is closed by a foil-like tear face cover 104 welded and/or crimped to a flange-like rim which extends laterally from the side-wall of cup 102. A capsule holder 111 comprises a flow grill 112 with relief surface element members 113 and an annular chamfered rim 114. The capsule holder 111 is accommodated in its support 115 which has a lateral wall 124, and a bore 127 for the passage of extracted coffee beverage.
As can be seen from FIG. 1, the extraction system further comprises a water injector 107 having a water inlet channel 120 and an annular element 108 with an internal recess of which the shape substantially corresponds to the outer shape of the capsule. On its outer part, the bell member 108 comprises a spring 122 holding a ring 123 for releasing the capsule on completion of extraction.
In operation, a capsule 101 is placed in the capsule holder 111. The water injector 107 perforates the upper face of the cup 102. The lower tear face 104 of the capsule rests on the radially arranged members 113 of the capsule holder 111. The water is injected through the channel 120 of the water injector 107 and impinges on the bed 103 of coffee. The pressure in the capsule 101 increases and the tear face 104 increasingly follows the shape of the radial opening relief members 113. When the constituent material of the tear face reaches its breaking stress, the tear face tears along the relief members. The extracted coffee flows through the orifices of the flow grill 112 and is recovered in a container (not shown) beneath the bore 127.
The principles of this extraction process as far as it can be maintained in connection with the present invention can be summarized as follows:
a sealed capsule is inserted in capsule holder;
the capsule holder is then associated with a water injection portion of the machine such that an annular element (108 in FIG. 4) surrounds the capsule;
in a first wall of the capsule at least one opening is generated, and
water entering the capsule through the opening in the first wall is interacting with the ingredients in the interior of the capsule and the thus produced beverage is then drained from at least a second opening is created in the second wall.
The ingredients in the capsule constitute the “bottleneck” of the flow path of the water and will therefore cause a pressure drop between the upstream and the downstream side of the liquid flow through the capsule, which pressure drop will even increase during the interaction between the liquid and the ingredients for example due to a swelling of the ingredients. Correspondingly it has to be assured that the only water flow is actually taking place through the interior of the capsule (arrow A1) and that no water can flow from the water injector into the interstice between the annular enclosing member 108 and the exterior of the capsule 101 and then to the draining bore 127 of the device. The arrow A2 illustrates this undesired external water flow path. With other words, any water flow exterior to the capsule 101 has to be stopped (or at least hindered to a substantial degree) by a sealing engagement being positioned in the interstice between the annular member 108 and the capsule 101 and in the flow path between the water injector and the beverage-draining bore. In the prior art embodiment shown in FIG. 1 such sealing engagement can be achieved by the pinching engagement between the annular member 108, the flange-like rim of the side wall of the capsule 101 and the capsule holder.
In case the sealing engagement is not working properly and water is flowing outside the capsule, no pressure sufficient to cause the tearing of the tear face will be built up inside the capsule, or alternatively, a too low pressure will be causing partial tearing of the tear face and therefore only a poor extraction of the substance, consequently, leading to the delivery of a low quality beverage. In such a scenario water will be drained from the beverage production device without having interacted or fully interacted under sufficient pressure conditions with the ingredients contained in the capsule.
New machines are now commercially available which are based on an axial closure movement and no longer on a bayonet-style closure. These machines provide more user convenience, they can be mechanically, electrically or hydraulically assisted for an easier closing and they can be made of less expensive materials (such as plastic). For instance, a few patents describe different closure principles such as in EP 0604615, EP 1090574; EP 1327407; WO 2004/071259 or WO 2005/004683.
Therefore, there is no possibility for the user to control the degree of tightening of the closure about the capsule. As long as the intrinsically defined closed state, of the devices working on an axial closure movement, is working properly, this leads to satisfying results. If, however, the seal has been damaged or its efficiency has decreased over time for different reasons (such as due to wear, ageing, obstruction by solid residue, etc.) or also, in the event, the closed position is misaligned (e.g., horizontally offset vis-a-vis the ideal closure position due to wear, fatigue or manufacturing tolerances), there is the risk of having no tight sealing or even having an undesirable clearance between the enclosing member and the capsule.
According to the prior art, sealing engagement is accomplished by lining the inner wall and/or pressing edge of the capsule cage with a rubber-elastic joint. In other words, according to the prior art approach, the sealing engagement is assured by a permanent structure which is fixed to or attached to the beverage-producing device. This has the disadvantage that after intensive use (i.e., over a high number of extraction cycles), a wearing off of the permanent seal can take place such that the extraction conditions of the beverage may deteriorate and quality of the beverage accordingly negatively affected.
In particular, any “leak” at the exterior of the capsule reduces the pressure inside the capsule. On the other hand, a sufficient extraction pressure is a key factor for the quality of espresso-style coffee. Thus, improvements in these type devices are desired.